What’s New in Research: April 2019

The Brigham is home to nearly 5,000 researchers, including physician-investigators, biomedical scientists, and faculty, who publish new research papers on a range of scientific and medical subjects. Below are brief summaries of a selection of our community’s most recent work. If you have an upcoming Brigham publication, please contact bwhclinicalandresearchnews@partners.org.

Food allergies, celiac disease, inflammatory bowel disease (IBD), diarrhea and other gastrointestinal diseases have something in common: all have been linked to epithelial barrier loss. The gut epithelial barrier—that critical lining of cells in the gut that must allow nutrients into the body while keeping food-borne microbes out—can be compromised during intestinal inflammation and cause disease. While many of the molecular mechanisms that trigger gastrointestinal diseases remain a mystery, previous research has found that one enzyme, known as myosin light chain kinase (MLCK), plays a critical role. However, MLCK is also essential for critical functions in gut epithelia and other cell types. This makes direct inhibition of MLCK impossible, as it would result in many toxic and systemic side effects. A team led by investigators from Brigham and Women’s Hospital has now developed an alternative approach. In a study published in Nature Medicine, the researchers report new evidence suggesting that specifically targeting one version of the enzyme—MLCK1—may be effective in both preventing and treating gastrointestinal disease by preserving and restoring barrier function, respectively.

“This represents a completely novel, non-toxic approach to intestinal barrier restoration and treatment of inflammatory bowel disease,” said corresponding author Jerrold Turner, MD, PhD, of the Department of Pathology at the Brigham.

Other forms of MLCK can be found throughout the gut lining, in various epithelia and in smooth muscle. But the MLCK1 isoform is particularly expressed in the villous enterocytes—intestinal cells that sit in the finger-like projections that extend into the lumens of the small intestine—and corresponding surface cells of the colon. To lay the groundwork for targeting only MLCK1, Turner and his team solved the crystal structure of the region that distinguishes MLCK1 from other variants. They then used computer modeling to screen approximately 140,000 molecules, looking for one that could dock into this region like a key in a lock.

The team found a molecule, which they named Divertin, that fit neatly into this pocket. Divertin (so-named because it diverts MLCK1 away from the intracellular sites at which it regulates the barrier) prevented inflammation-induced barrier loss without compromising key MLCK enzymatic functions in epithelia and smooth muscle. In mouse models of inflammatory bowel disease and diarrhea, Divertin corrected barrier dysfunction and reduced disease severity. When given prophylactically, Divertin prevented disease development and progression. This suggests that Divertin might be a new, non-immunosuppressive means to maintain remission, and prevent disease flares, in patients with IBD.

Turner and colleagues note that targeting MLCK1 to prevent barrier loss and restore function could also be useful in other diseases where the epithelial barrier is compromised, including celiac disease, atopic dermatitis, pulmonary infection and acute respiratory distress syndrome, multiple sclerosis, and graft versus host disease (GVHD). In a study published recently in The Journal of Clinical Investigation, the same research team presented evidence that MLCK drives the continuation of GVHD, a complication that can arise after a transplant when donor immune cells begin attacking the organs of a transplant recipient. While Divertin was not tested in GVHD, the data suggest that it may be an effective therapy.

“Our study indicates that MLCK1 is a viable target for preserving epithelial barrier function in intestinal diseases and beyond,” said Turner. “This therapeutic approach may help break the cycle of inflammation that drives so many chronic diseases.”

Funding for this work was provided by the National Institutes of Health (R01DK61931, R01DK68271, P30CA14599, P30DK034854, and T32HL007237), the Broad Medical Research Foundation (IBD-022), the Department of Defense (W81XWH-09-1-0341), a Catalyst Award from the Chicago Biomedical Consortium, and the National Natural Science Foundation of China (81470804 and 31401229). The Berkeley Center for Structural Biology is supported in part by the National Institutes of Health, National Institute of General Medical Sciences, and the Howard Hughes Medical Institute. The Advanced Light Source is a Department of Energy Office of Science User Facility under Contract No. DE-AC02-05CH11231.

When one thinks of carbon monoxide (CO), the picture that comes to mind is not usually therapeutic in nature. CO’s lethal effects are well known. When inhaled at large enough doses, CO causes carbon monoxide poisoning, which kills 400 Americans each year and leads to more than 20,000 visits to the emergency room, according to the Centers for Disease Control. But what if, at a lower dosage, inhaled carbon monoxide (iCO) had the potential of being a safe treatment for a life-threatening lung condition? This question drove a group of researchers from Brigham and Women’s Hospital to conduct a Phase I study to investigate the safety and feasibility of administering low-dose iCO to patients with sepsis-induced, acute respiratory distress syndrome (ARDS). The study is the first clinical trial to assess low-dose iCO as a potential therapy for critically ill patients. The results are published in the journal JCI Insight.

“Low-dose iCO has been found to be protective in a number of animal models of sepsis and acute lung injury,” said Laura Fredenburgh, MD, corresponding author and physician in the Division of Pulmonary and Critical Care Medicine at the Brigham. “I’m an intensivist who provides clinical care for patients who are critically ill in our Medical Intensive Care Unit. Some of the most common diseases we see in the ICU are sepsis and ARDS, both of which have significant mortality. Particularly for ARDS, we have no pharmacologic treatment and the mortality rate is exceedingly high.”

In the body, CO is produced by an enzyme called heme oxygenase-1 as part of the physiological breakdown of heme — a sub-unit of hemeproteins, such as hemoglobin (Hb). At high levels, CO can become pathological, binding Hb with higher affinity than oxygen and co-opting the body’s oxygen delivery system. But at low levels, CO exerts restorative effects, including suppression of inflammation, protection against cell death, and enhancement of phagocytosis, a critical component of the body’s immune system. All of these processes are crucial to the resolution of sepsis and ARDS.

While the safety and effects of low dose iCO have been previously investigated in preclinical models and healthy volunteers, this is the first time it has been studied in critically ill ARDS patients.

“The reason why it’s taken so long for inhaled CO to get to clinical trials is that it has a narrow therapeutic window,” Fredenburgh said. “At high doses, it can be toxic, so being cautious is very important.”

To assess the clinical safety and feasibility of low-dose iCO treatment, Fredenburgh and colleagues at the Brigham, MGH, Weill Cornell, and Duke conducted a dose-escalation trial in patients with sepsis-induced ARDS. Participants were randomized to receive either iCO (100 ppm or 200 ppm) or placebo air for 90 minutes daily for up to five days. Given the Phase 1 nature of the trial, the investigators carefully monitored safety-related outcomes including the patients’ carboxyhemoglobin (COHb) levels, an indicator of the percentage of Hb bound by CO, and incidence of adverse events.

The team found that there were no study-associated severe adverse events, and all participants tolerated the treatment and procedures well. Those receiving iCO had COHb levels not exceeding 7 percent — remaining well below the established safety threshold of 10 percent COHb. Furthermore, there was a dose-dependent, predictable increase in COHb levels.

“Our study showed that low dose iCO could be safely administered in critically ill patients and that we could accurately predict how much of the drug was being taken up in patients with lung injury,” said Fredenburgh. “This was an important finding for us as it gives us additional assurance that as we move forward with this potential new therapy, we have a number of safety measures that we can follow.”

Currently, Fredenburgh and colleagues are preparing to launch a Phase II safety and efficacy study in patients with sepsis- and trauma-induced ARDS, funded by the Department of Defense, and tentatively scheduled to begin enrollment in April.

“That we were able to translate this research bench-to-bedside — from cells, to large animal models, and now to a Phase I clinical trial and a future efficacy study — that’s exciting,” said Fredenburgh. “Our hope is that low dose iCO will reduce the severity of lung injury and accelerate recovery from sepsis and ARDS.”

Funding for this work was provided by the National Institutes of Health (NIH) grants P01HL108801, KL2TR002385, K08HL130557 and K08GM102695.

Study finds that tighter networks of family members restricted information flow, delayed arrival time for those in need of life-saving care

Newly developed treatment strategies can minimize the size of a patient’s stroke and, in many cases, change what would have been a life-altering cerebrovascular event into a minor one with the prospect of excellent recovery. But these therapies are time sensitive — delays in seeking care can put them out of reach. Each year in the U.S., 795,000 patients will have a stroke and approximately 70 percent of them will arrive at the hospital more than six hours after the onset of symptoms. Investigators from Brigham and Women’s Hospital examined how social networks may influence delays in arrival times for patients experiencing the symptoms of a stroke. Paradoxically, they found that patients with closer-knit social networks, including family members and spouses, were more likely to delay seeking hospital care whereas those with a more dispersed network of acquaintances were more likely to seek care faster. The team’s analysis is published in Nature Communications.

“Closed networks are like echo chambers in which there is a tendency for everyone to agree to watch and wait,” said corresponding author Amar Dhand, MD, DPhil, of the Department of Neurology at the Brigham. “A major problem in stroke care is patients’ delayed arrival to the hospital, and we show that this problem is related to the influence of patients’ social networks.”

Dhand and colleagues surveyed 175 patients within five days of suffering from a stroke. They collected information from each participant about personal social networks, creating network maps. The team focused on patients with milder symptoms because this population is at higher risk for delay and were able to engage in the survey during hospitalization.

They found that the networks of slow arrivers were smaller and more close-knit than those of fast arrivers, confirming a paradoxical role for a person’s social environment in a medical emergency. The authors concluded that a shift from mass education about stroke symptoms to a more targeted approach may help reduce delays. Identifying at-risk patients with small and close-knit networks before a stroke and teaching them about symptoms and communication pitfalls as well as helping them develop an action plan, which might include calling a designated friend, could improve stroke preparedness and outcomes.

The current study was limited mainly to patients who had had a mild stroke and it remains to be seen if social networks play as large a role for delays in care for a moderate or severe stroke. The survey did not include non-English speakers or patients with severe strokes or aphasia. The study also relied on self-reporting of social networks. The authors note that additional study in more diverse populations is warranted.

Funding for this work was provided by the National Center for Medical Rehabilitation Research (K23HD083489), American Heart Association (14CRP20080001), National Institute of Diabetes and Digestive and Kidney Diseases (P30DK046200), National Institute of Neurological Disorders and Stroke (R01NS085419), and the Football Players Health Study at Harvard University.

Charles Serhan (far right) and members of his team work to discover molecules that are critical for terminating and resolving acute inflammation.

Researchers Show Aspirin Boosts Production of an Anti-Inflammatory that Inhibits Tumor Growth

About half of all Americans 45 years and older and older take a low dose of aspirin daily either to reduce the risk of a second heart attack or stroke or prevent a first one, a practice dating back to the 1940s. Since then, strong epidemiological evidence has also suggested that a daily dose of aspirin, an anti-inflammatory drug, may reduce the risk of cancer by up to 30 percent. However, daily aspirin also increases the risk of bleeding, limiting its use as a cancer preventing medication.

In a new study published this week in the Proceedings of the National Academy of Sciences, scientists led by Dipak Panigrahy, MD, of the Cancer Center at Beth Israel Deaconess Medical Center (BIDMC) and Charles N. Serhan, PhD, DSc, director of the Center of Experimental Therapeutics and a member of the Department of Anesthesiology, Perioperative and Pain Medicine at Brigham and Women’s Hospital, demonstrate a unique new mechanism by which aspirin inhibits cancer.

Working with multiple preclinical cancer models, the team demonstrated that aspirin both blocks production of compounds that promote inflammation and triggers the production of naturally occurring anti-inflammatory factors produced by the human body called resolvins. Resolvins were first discovered by co-corresponding author Serhan and colleagues at the Brigham in 2002.

In study, aspirin-triggered resolvins inhibited primary tumor growth by enhancing the immune system’s ability to clear the body of tumor cell debris. (In a 2017 study, Panigrahy, Serhan and colleagues showed that debris from cancer cells killed by chemotherapy can promote new tumor growth.) When the scientists treated the tumor-bearing mice with aspirin-triggered resolvins alone in the absence of aspirin, they found it inhibited primary tumor growth in a variety of tumor types and at low concentrations.

“We were surprised at the potency of the aspirin-triggered resolvins in blocking tumor growth – they exhibited anti-tumor activity at much lower concentrations than aspirin in preclinical models,” said Panigrahy, who is also Assistant Professor in the Department of Pathology at Harvard Medical School. “These results have pivotal implications for cancer therapy and chemoprevention. Aspirin-triggered resolvins may be harnessed to mimic aspirin’s potent anti-tumor activity without running the risk of aspirin-related toxicity.”

“These are exciting results with potential implications for care and treatment,” said Serhan. “As our understanding of resolvins deepens, novel functions and applications are emerging that will merit clinical investigation.”